In the art of animal husbandry and particularly in the feeding of swine, it is known to provide so-called ad libitum fodders or hog-feed compositions which contain indigestible extender components in the form of particles or granules.
The indigestible additive generally is foamed and granulated synthetic resin with a particle size upwards of 5 mm which is used to establish a predetermined bulk weight of the fodder or food composition, which increases the bulk of the food product and which does not detrimentally affect the digestive process as much as possible.
The problems involved in preparation of such fodders, i.e. fodders containing foamed and granular synthetic resins of the indicated particle size range, are those which are associated with separation of the components of the feed mixture, the problems of handling and manufacturing the animal feed because of the increase in volume resulting from the use of the additive, and problems which are associated with the dispersal of the animal dung.
However, when synthetic-resin materials are used, it is not possible to exclude detriment to the digestive tract and thus the health of the animal which, of course, affects the quality of the meat because unreacted chemical components of the synthetic resin, softeners and plasticizers may leach or otherwise be solubilized from the synthetic-resin materials.
In addition, the synthetic-resin additives may have a pH value or, in the digestive tract may produce a pH value, e.g. in the highly acid range, which is detrimental.
Difficulties have also been found to arise with the use of such additives when the excrement and urine of the swine are to be utilized as fertilizer and dispersed on the fields. The granular additives of foamed synthetic resin are not easily decomposed and this applies whether the dung is applied in a dry state or wet.
While it is true that some granular porous foamed synthetic resins are desirable in loosening the soil, they have scarcely any water storage capabilities and thus do not even have the capacity of absorbing valuable fertilizer components for releasing them gradually to the fields. This may be a result of the hydrophobic character of the synthetic resin and/or a closed pore structure as is usually provided.